First thing I do when I get to the Boat launch is go to the back of the boat and install the drain plugs, then install/connect the rudders, then untie the mast from the rear crossbeam, Girlfriend unties the front of the mast, then shroud/trapeze lines, I pull them back and untangle, climb on the tramp, she goes to the back and grabs the mast and we walk it back to stand, never changes, never will. Keeps us from getting tangled up and forgetting something.

I've made a little choreography sheet to help use setup time better, and drain plugs are the crew's job. Probably should happen right before rudder installation. But the final walk-around before the boat goes down the ramp should cover them also.

I don't think there's anything wrong with a tell-tail system like the OP mentioned but a heavy flapping streamer would make me nervous on the road since I'm going up to about 80MPH.

EDIT: maybe a streamer that is connected to the gudgeon world work. That way you have to acknowledge the drain plug if you want to install the rudder.